PROJECT SUMMARY Tobacco use and exposure to secondhand smoke (SHS) are the leading preventable causes of morbidity and mortality in the US and worldwide. There is no safe level of tobacco smoke exposure. In just 4 years, from 2009 to 2012 (the most recent data available), cigarette use among US individuals aged 18-24 (the age group most likely to use cigarettes or hookahs) decreased by 8.4% to 5,254,500. In marked contrast, hookah (e.g. waterpipe) use in the last 30 days increased 142% in the same time period, to 5,745,690. This highlights that hookah use is increasing at a far greater rate than cigarette use is declining, such that the number of hookah users in this age group is now greater than the number of cigarette users. Should current trends persist, the number of hookah smokers across the entire age spectrum in the US will increase greatly. This has led to widespread public health concern that hookah use may eradicate most or all of the profound decrease in tobacco use achieved over the past 60 years. In the proposed study, we focus on hookahs, as they have been the most widely adopted alternative tobacco product (ATP). There is a profound paucity of data on its effect on household ambient air quality and the health of individuals exposed to mainstream, e.g. smoke derived from actually smoking, and SHS in such homes. This contrasts markedly with the extensive knowledge base on related issues concerning cigarettes. We and others have demonstrated markedly poor indoor air quality in hookah bars, with significant elevations in particulate matter, black and organic carbon, carbon monoxide, nicotine and multiple trace elements of concern. A related but still rudimentary research literature is emerging showing both acute and long term negative consequences of active and passive exposure to hookah smoke. The CDC, FDA, and the American Lung Association each has expressed grave concerns about hookah use and The Surgeon General has noted that the most important environmental tobacco smoke exposure for children occurs in the home. The proposed study will investigate potential deleterious alterations in ambient air quality in homes where hookahs are smoked, and selected aspects of the health of both children and adults residing in homes where hookah smoking occurs, and compare results to the air quality and health for those living in homes without hookah smoking. We hypothesize that ambient air quality is detrimentally altered in homes where hookahs are smoked, and that inhalation of SHS generated by such hookah smoking results in adverse pulmonary and cardiovascular effects in residents of such homes. Findings from this study will likely have very significant research, clinical and policy implications by enhancing understanding of this profoundly important and currently understudied area concerning the most widely adopted and fastest growing ATP in the US.